1. Field of the Invention
The present invention relates to a leak noise correlator apparatus for determining the location of a leak in a fluid-carrying conduit, particularly in an underground water pipe.
2. State of the Art
It has been known for a long time that water or other fluid escaping from a pressurised pipe generates a characteristic noise at the location of the leak. This characteristic noise is propagated along the pipe in both directions from the leak location and with equal velocity. It has also long been known to determine the leak location quite precisely by coupling acoustic transducers to the pipe on either side of the leak: the leak noise is received by both transducers but with a time difference which depends on the distances of the transducers from the leak location; the location of the leak can accordingly be determined as a function of this time difference. U.S. Pat. No. 4,083,229 (Anway) discloses an apparatus which receives electrical signals from the two transducers and performs a cross-correlation of these two signals to determine the time difference between the characteristic leak noise in these two signals and accordingly determine the location of the leak.
Hitherto, leak noise correlator apparatus have employed a pair of acoustic transducers either connected to it by means of cables or transmitting their output to it as radio-frequency signals. However, practical difficulties arise in connecting the transducers to the apparatus using cables, because the transducers are often coupled to the pipe at considerable distances apart and it may be physically difficult to run the necessary cables, especially in busy city centres. For radio transmission, the apparatus is limited by the quality and cost of the radio communication equipment required: also, under certain jurisdictions, the maximum output power may be severely limited; also, the licensing of radio frequency equipment may be limited.